Creep prevention control for hydraulic power units



June 9, 1953 s. A. JACQUES 2,641,227

CREEP PREVENTION CONTROL FOR HYDRAULIC POWER UNITS Filed Nov. 13, 1950 4Sheets-Sheet l l" n ""I N SeZecz pr L 1? Valve i N J 1 INVENTOR.

June 9, 1953 s. A. JACQUES 2,641,227

CREE? PREVENTION CONTROL FOR HYDRAULIC POWER UNITS Filed Nov. 13, 1950 4Sheets-Sheet 2 June 9, 1953 s. A. .mcauzs 2,641,227

CREEP PREVENTION CONTROL FOR HYDRAULIC POWER UNITS Filed Nov. 15, 1950 4Sheets-Sheet 3- June 9, 1953 s. A. JACQUES 2,641,227

CREEP PREVENTION CONTROL FOR HYDRAULIC POWER UNITS Filed Nov. 13, 1950 4Sheets-Sheet 4 w v i ll] Patented June 9, 1953 action UNITED STATESPATENT OFFICE cRE'EP PREVENTION CONTROL FOR HYDRAULIC POWER 'UNITSStanley A. Jacques, Chicago, 111., xassignnr gto Aska'nia RegulatorCompany, Chicago, 111., .a corporation of Illinois Application November13, I950, =Ser ia1l'No. 195,3 7 8 9 Claims. l

The present invention relates to systems and mechanisms for preventingsubstantial creeping movement of the output member :of a hydraulic powerunit slur-mg cutoff of supply of operating fluid to the unit. By creepis meant movement of the member driven by hydraulic fluid. supplied tothe unit, permitted 'by seepage of fluid loetween opposed and.theoretically .rluid tight surfaces "of "the movable memberand'stationary structure :of the unit. .A cylinder and piston assemblyis a typical power unit of the kind question, and the inmtion disclosedas used with such an assembly, that-obviously it is readily applicableto other kinds of hydra-idle power units, such as rotary .cluid motorsthat are .re-

verstbl'e =by selectively supplying pressuce to one of two input ports.

In'a'ny power system having a hydraulic power output unit thatiscontrol-led by supply or cutoff of operating fluid, it may he:tl'esiralole to arrest and'maintain the unit inn-a selected position.if the load on the unit .is of a kincl that exerts force when arrested,the unit tends to creep :by seepage of the operating fluid betweenopposed melatively movable surfaces, as by seepage past 'a piston,thereby permittm 1 -;e load "to drive the power unit eyen though power,i'luidinlet vis blocked from supply. The invention :is directed toovercoming condition. ,Breyiously, ef-

icrts have been made to lock. h-yrlraulic gposver units againstcreeping, by means of brakes or clutches, actuable to engage a movableunit element, thereby to lock the unit-and.- its. load (in -:-anarrested-position. Various \clisaclventages are ten? countered in theemployment of such brakes and clutches; The present .inyentionprouiclesfor an auxiliary supplyof operating fluid to a reversible power unit,'whiohausiliary.supply is established when the :unit is 'aririestecl byblocking of itSrIlQl' mal operation supply, and which is controlled in.response to yery lsl-ight creepi-ng of the .unit output to supplyoperating fluid in .a sense to return the unit and .itsiload to the:selectedpos'ition in which iter-as tar-rested. Ehe invention also isdirected to a unitary assembly for association with a hydraulic pistonand cylinder for :accomplishing an anti-creepcontcolinaccordance .withthe broader aspect "of the invention outlined above.

A'primary object of "the invention is the provision of a novel "systemfor preventing substantial creeping "movement of the output member of 'ahydraulic power unit when the latter has been arrested by blocking ofits fluid supply.

Another object is the provision in ta :hyditawlically powered relay orpower amplifier system of "a noyel (arrangement of an auxiliary powerunit supply that "is responsive to creeping movement of an output memberof the unit to sup ply operating fluid to the unit to restore its outputmember to a :selectedposition in which it has been arrested by bloc-kingof .its main, controlled fluid supply.

Another woloject is the provision of such a sys- :term with a novelcontrol system that automatically correlates operation of all systemelements necessary to set up either a normal condition of controlledpower unit operation or a second oonclition wherein the auxiliary,anti-creep system is in control :of the power :A further object is .theprovision of a novel system for placing an auxiliary anti-creep controlwaive in control of a reversible ,power unit when a condition ofresponsiveness to movement of the output member of such power unit.

Aniadditional \objectis the provision .of a novel unitary assembly forassociation with a hydraulicallyeoperated pistonnand cylinder unit andcontaining all hydraulic valve elements and control means therefor thatare necessary to act as a system for restoring thepistonto a selectedpositionin Whichfit .is to be maintained during its (Alt-:Qfi iromiitsmainfhydraulic operating system. ,stillianother object is the provisionof anovel hydraulic relay arrangement for actuating a two-positionaxially .moyable valve body.

iIHTthe accompanying fclrawings:

fig. 1 is .a schematic diagram of ,a complex hydraulic zrelay systemprovided with an auxiliary anti-creep or creep-controlxsystenrarrangedaccording to the intention, and showing the normesl :oper-a-tingcondition with the auxiliary system disabled. Fig. T2 is :a partialschematic diagram showing only't-he auxiliary anti-creep system in itseffective condition. 1 Fig. 3 is a'partiallybrokentop planet a uni-Ltary assenib-ly that provides the anti-creep system 'o'fFigs. 1 and 2,an'd'is specifically adapted Jfor association with a piston and cylinderby- .draul 'icpower unit.

Fig. l is a transverse Vertical section on "line rfi 4 rof Fig. .3 andFig. 5.

Big. .5 is a longitudinal section on line 5- 5 of Fi .4.

:Fig. (-6 is an elevation .of .the right end of the unit as seen in.rliig. .3 or Fig. 5.

Fig. 7 :isajlong-itudinal vertical-section on line ii of.,l lig. 16

Fig. 8 is a vertical transverse section on line 8--8 of Fig. '7.

Fig. 9 is a vertical transverse section on line 99 of Fi 3.

Fig. 10 is a vertical transverse section on line |0l0 of Fig. 3 and Fig.5.

Fig. 11 is a vertical transverse section on line |I|l of Fig. 1.

Fig. 12 is a vertical section on line |2|2 of Fig. 5.

Reference is made to my copending application for United States patent,Serial No. 184,972, filed September 15, 1950. That application disclosesand claims a hydraulic power unit control system wherein selection maybe made of control by a relay regulator or by a manually operableselector valve. The regulator and manually operable valve respectivelycontrol flow of fluid between supply, the power unit and exhaust throughdifferent parallel channels. The relay controlled channel includes acutoff valve that is actuable by the manually operable selector valve tocorrelate blocking and unblocking of the relay channel with operation ofthe selector valve to actuate and not actuate the power unit through themanual control channel. This system has been selected for disclosure ofthe present invention, because the manual control channel of the priorsystem provides a convenient arrangement for supply of the anti-creepsystem in situations ,where controls must be remote from the power unit.The prior system is schematically disclosed in Fig. 1 in suchassociation with the anti-creep system of the present invention.

In Fig. 1 a main fluid supply line is designated l0, and is the sourceof supply of operating fluid delivered under pressure to actuate such apower unit as a piston II in a cylinder [2. Cylinder lines [3, I4communicate with opposite ends of cylinder l2 for selective andreversible connection of one with supply line H) and other with a systemexhaust. Connected with supply line I I] are the channel supply lines 16and I! that respectively deliver fluid to the manual, and the relay orautomatic channels that actuate piston ll through controlling supply offluid to cylinder lines I3, 14. The manual channel includes a transfervalve l8 that is actuable by manual operation of a selector valve 19, toconnect selectively and reversely one of channel outputlines 20, 2! tosupply line l6 and exhaust the other toa channel exhaust 24, or toblockboth lines 20, 2| from both lines I6, 24. Channel output lines 20, 2|respectively are connected to system output lines 22, 23.

The relay or automatic control channel includes a relay regulator thatis automatically operable by some signal toselectively and reverselyconnect one of a pair of channel lines 26, 21, which are connected tothe system output lines 22, 23, with channel supply line I! and exhaustthe other to a channel exhaust 29. The relay channel also includes acutoff valve 28 connected in series between channel lines 26, 21 andchannel output lines 30, 31 and actuable between an inactive conditionconnecting line to line 25 and line 3| toline 21, and an activecondition blocking such connections.

By relay connections represented by dotted lines 32 in Fig. 1, operationof selector valve l9 by a hand operator 33 actuates transfer valve 18and cutoff valve 28 in correlated manner, to block the manual channeland unblock the automatic channel by movement of operator 33 to anautomatic position designated A, to block both chan- 4 nels and therebystop the power unit by movement of the operator to a "neutra position,three of which are designated N, or to block the automatic channel andunblock the manual channel by connecting a selected one of channeloutput lines 20, 2| to supply and the other to exhaust, accomplished bymoving operator 33 to positions designated L and R which respectivelyindicate leftward or rightward movement of piston II.

The present invention relates to an auxiliary anti-creep system that maybe made efiective, after stopping a hydraulic power unit as by movingoperator 33 of Fig. 1 to an N position, to re spond to creeping of thepower unit from the position in which it is stopped to return the powerunit to that position.

Referring to Figs. 1 and 2, it will be seen that a piston rod 35 issecured to piston II, and this rod serves as the output member of thepower unit. Basically, the anti-creep system of the invention comprisesan auxiliary fluid supply and exhaust, an auxiliary control valve forselectively connecting one input port of a reversible hydraulic powerunit to an auxiliary power fluid supply and the other to exhaust, andvalve and clutch mechanisms actuated in correlated relation respectivelyto establish the auxiliary supply to the auxiliary control valve, and tocouple the latter to the movable power unit output member for actuationby it, in a sense to supply the power unit in a sense to actuate theunit in the opposite direction to the creeping movement actuating theauxiliary control valve.

Returning to Figs. 1 and 2, an auxiliary rod member 36 is attached topiston rod 35 at a point that always is beyond the adjacent endstructure of cylinder I2, as by a simple clamp 31, for movement with andparallel to piston rod 35. A gripping device 38 is selectively actuableto release, or to clutch itself to rod member 36 for movement with it.Gripping device 38 is, by a transmission rod 39, connected to operate anauxiliary control valve 40. This valve 40 constitutes the control deviceof the anti-creep system and acts, during clutching of device 38 to rod36, and upon movement of rod 36, to connect to an auxiliary controlvalve fluid supply line an end of cylinder ll toward which the pistonhas moved, or is moving, and to connect the other cylinder end to anauxiliary control valve exhaust line.

While practice of the invention as so far described may be accomplishedby supply of fluid to the auxiliary control valve supply line by a fluidsystem that is completely auxiliary to, and turned on and offindependently of the main power unit supply and control system, for minimizing piping connections and positively correlating the elementactuations necessary to fully activate either the anti-creep or mainsystem, and to place the activated system in sole control of the powerunit, it is desirable to provide for supply to the auxiliary controlvalve through the main system. The system now to be describedexemplifies a system type forming a second important aspect of theinvention.

An auxiliary transfer valve 45 is connected between the system outputlines 22, 23 and the cylinder lines l3, l4. Transfer valve 45 isactuable between a normal condition, shown in Fig. 1, connecting line l3to line 22 and M to 23, and an anti-creep position, shown in Fig. 2',blocking such connections, thereby cutting off the cylinder from directcommunication with the main accuser control system, but also connectingan auxiliary control valve supply line 46 with a preselected one of themain system output lines '22, '23. In the arrangement shown in Figs. 1and 2, the preselected main system output line is 23, and it iscontemplated that, for activation of the amtiliary anti-creep system nowbeing described, the main system will be conditioned by appropriatepositioning of operator '33 and actuation of trans fer valve 18, toconnect line 23 with supply line I6 and line 22 with exhaust line 24. Inthe arrangement shown, the body of auxiliary transfer valve is movablefrom a normal-operation position, shown in Fig. 1, leftward to ananticreep position shown in Fig. 2. The spool body of valve 45 comprisesa center land 41 that "is movable between the Fig. 1 position blockingauxiliary control valve line 46 and providing communication of cylinderline I 3 with system line 22, and the Fig. 2 position providingcommunication of auxiliary control valve supply line 45 with system line23. r A second land 48 is movable between the Fig. 1 position providingcommunication of cylinder line I4 with system line 23 and the Fig. 2position blocking cylinder line H. A third land 49, and land 43,bothblock the end portions of the bore 55 in which the spool body isslidable. The body of transfer valve 45 is biased to one of itspositions, preferably the normal operating Fig. 11 position as shown, bya spring 5|. While an auxiliary system exhaust might be arranged similarto the .supply system for establishment and disabling of the auxiliarytransfer valve, for simplicity an auxiliary exhaust system ispermanently in communication through a line 52 with the main systemline, here 22, that is connected to exhaust for anti-creep operation.The end portion 53 of the transfer valve bore 5%) beyond land 49 whereinto line 52 by a bleeder connection 54. The opposite end portion 55 ofthe auxiliary transfer valve bore 50, wherein part 48 is slidable as apiston, is selectively connectible, for normal operation to the samesystem line, here 22, as is bore portion 53, and for anti-creepoperation to the other system line, here 23. By this means, in normaloperation, a condition wherein the pressure differential between lines22, 23 frequently is varyingly unbalanced and static pressure in .line22 is fluctuating. equal pressures act oppositely on the outside ends oflands 48, 49, effectively cancelling out each other and permitting biasspring 5! to maintain the transfer valve body in its position for normalmain system operation of 1 the power unit. When the two bore ends 53, 55are connected to the diiferent system lines 22, 23, and the latter areconnected to act respectively as supply and exhaust lines for anti-creepoperation, the resulting unbalanced pressures on the outer ends of lands43, 49 move the valve body to its second position. Connection of the twobore ends 53, 55 to the same one of lines 22, 23 provides bleed pathsfor fluid that may escape to the bore ends by seepage past lands 48, 49durin normal operation. For selectively connecting the second end '55 ofbore to lines 22, 23, a three-way relay valve 56 is provided, inarrangement to select the one of lines 51, 58, which respectivelycommunicate with system lines 22, 23, is connected to a controlled line59 that leads to the valve bore portion 55. A solenoid 6G is arranged tomove the body of relay .Valve to one position when energized, con- Bnectlng controlled line 5.9 to OIIG'JOf 5.1, 5155, and :a bias spring5-] :is arranged ".to :move the valve body when solenoid 60 .deenergizedto a second position connecting vthe other of lines 51, 58 to line 59.In the arrangement shown, the deenergized solenoid condition :Of Fig. 1provides normal operation by connecting system output lines 22, 23 withcylinder lines [3, =14. The :solenoi'd :and .relay valve arrangement'50, 156, 16] *is employed :to provide adequate forcefor operating froma remote control station of an auxiliary transfer valve located at thepower unit and in cluded :in an assembly arranged for installation atthe power unit and which is to be described later.

Gripping :device 35, for similar remote control purposes, preferably issolenoid operated also.

Any electrically actuated clutch device may be employed as device 38. Asshown schematically by Figs. 1 and 2, a solenoid 65 and a biasing spring66 are arranged to move an actuating lever 61' that is fulcrumed in acarriage 58 for gripping or releasing rod member '35. In the form shown,spring 56 and solenoid 55 are arranged to grip and release member 35respectively as the solenoid is energized and deenergized. A link 58pivoted at its opposite ends to the armature of solenoid '65 and lever5! permits movement of the latter withrod member 36 when th solenoid ismounted stationary. Such movement is limited, but is su'fi'lcient tooperate the auxiliary control valve 40, the valve operating rod 39 beingsecured to carriage 68. For correlating actuation of auxiliary transfervalve 45 and gripping device 38, solenoids 60, 65 preferably areconnected by common circuit means 69 to a control switch 15. Switch Illmaybe located at an operating station 1! and associated with manualoperator 33 in a desired manner.

Auxiliary control valve 48 comprises a conventional three-way spoolassembly of which the valve body is movable in a valve bore 13, from aneutral position shown in Fig. 1 and blocking communication betweenoutput lines 14, from communication with both auxiliary control valvesupply line 45 and an auxiliary control valve exhaust line 16, inopposite directions to connect one output line with line 46 and theother with line '16. Auxiliary control valve output "lines T4, 15constitute auxiliary cylinder lines and are connected with main cylinderlines l3, 14 in proper relation to supply fluid to the end portion ofcylinder ll toward which piston I2 moves while auxiliary transfer valve45 is in its anticreep position and lever 61 is in rod membergripp'ingcondition. A, return spring 1! biases the auxiliary control valve bodyto its neutral position.

A second aspect of the invention relates to a mechanical arrangement ofan auxiliary anticreep system, such as that shown in Figs. 1 and 2, as aunit designed to be associated with a piston and cylinder unit forcooperation therewith in the indicated manner. Such a unit, arranged inaccordance with this second aspect of the invention, is shown in Figs. 3to 12.

The unit comprises a main structure including a body member thatcontains the auxiliary transfer and auxiliary control valve bores 50,13.. and passage bores providing the majority of the lines of theanti-creep system, the remainder of such lines being provided by boresand grooves in end caps :81, :82 and in a base structure 83 of theassembly containing solenoid 60 that actuates relay valve 58. Body 88advantageously has feet 84 for attachment of the unit to a cylinderstructure forming part of a power unit provided with a rod, as 36, thatis moved by the piston of such assembly.

As shown by Figs. 3, and 6, the main structure includes a supportportion 85 that extends laterally of body 88 and projects longitudinallythereof beyond end cap 82. To this support portion 85 is secured abracket 88 that supports the coil 81 of the gripping device-actuatingsolenoid 85.

In the form of gripping device 38 shown in Figs. 3, 5, 6 and 9, thecarriage 68 comprises a body 88 having therein a bore in which aresilient split ring 89 is mounted and secured against axial movementrelative to the body, as by set screw 98. Split ring 89 encircles rodmember 38 and the ring and the bore containing it are so formed that inits undistorted condition the ring and the rod member relatively arefreely slidable. Lever 61 is fulcrumed to carriage body 88 to compressring 89 upon rod member 36 when lever 61 is actuated to its anti-creepposition, thereby clutching to member 36 the carriage and auxiliarycontrol valve rod 39. The latter has its end secured in a lateralextension 9| of the carriage body. Only a small gripping force isnecessary to accomplish operation of an auxiliary control valve from rod36, and adequate force can be developed from a conventional solenoid byproperly proportioning the lengths of arms of lever 61.

In one lateral surface of the main body member 88 are two input openings92, 93 for connection to output lines, as 22, 23, of a hydraulicregulator or other control system, such as that of Fig. 1, that iscapable of being conditioned to supply fluid under pressure to opening92 and to connect opening 93 to exhaust. In the opposite lateral surfaceof body member 88 are two output openings 94, 95 for connection to powerunit cylinder lines, as I4, I3 of Figs. 1 and 2. A first main input port91 in transfer valve bore 58 is formed by the end of a main passageway98 that communicates with input opening 92, and a second transfer valvemain input port 99, axially spaced from port 91, is formed by the end ofa main passageway I88 that communicates with input opening 93. Sincepassageways 98, I88 are connected to supply and exhaust lines foranti-creep system operation, hereafter they will be called main supplyand exhaust line passageways." In axially spaced relation to each otherand to input ports 91, 99, a pair of main controlled ports I8I I82 entertransfer valve bore 58 and communicate respectively with main outputopenings 94, 95 by passageways I83, I84 that are termed "main power unitsupply and exhaust passageways. An auxiliary controlled port I85, formedby the end of the auxiliary control valve supply passage 46, enterstransfer valve bore 58 in such axially spaced relation to all of ports91, 99, ml, I82, and to valve body land 41, as to be blocked when lands41, 48 provide communication between ports 91, I8I and ports 99, I82,and to be placed in communication with port 91 when the valve body hasbeen shifted to its anti-creep position wherein lands 41, 48respectively block main output ports I82, I8l.

Auxiliary control valve supply passage 46, which comprises a transversebore in body 88, forms a supply port I81 in auxiliary control valve bore13. A pair of exhaust ports I88 enter auxiliary control valve bore 13 atpoints axially spaced to opposite sides of supply port I81, andcommunicate with a longitudinal passage bore I89 that forms a branch ofan auxiliary exhaust system and that enters the end portion of auxiliarycontrol valve bore 13 containing return spring 11. An auxiliary exhaustpassage bore II 8 that extends longitudinally through body member 88 isconnected with main exhaust passageway I88 by a passage I II that may betaken as corresponding to auxiliary exhaust line 52 of Figs. 1 and 2. Apocket H2 in end cap 8I registers with one end of auxiliary exhaustpassage bore H8, and is connected, by a bleeder groove H3 cut into theinner surface of end cap ill, with a pocket II 4 that registers withauxiliary control valve bore 13. Pocket I I2 also is connected with apocket H5 in end cap 8| that registers with transfer valve bore 58 by ableeder groove II 6 that corresponds to bleeder line 54 of Figs. 1 and2.

Controlled ports II1, II8 of the auxiliary control valve communicaterespectively with main output passageways I8I, I82 by passages II9.Advantageously, an elongate inner shell I28 is mounted in auxiliarycontrol valve bore 13, with the auxiliary control valve body operatingin a central bore I2I in the liner, and ports I81, I88, I I1, I I8 andpassage I89 are machined in it.

Body member 88 is provided with a relay valve supply passage I26 thatextends from main supply passageway 91 to the end of the body that iscontacted by cap plate 82. Cap plate 82 has through it a relay valvebore I21 that is aligned with a valve pocket I28 in the adjacent end ofmain body member 88, and with a bore I29 in the base structure 83 ofsolenoid 68. Return spring BI is mounted in bore I29 to bias the body oftransfer relay valve 58 as described above. Cap plate 82 also has cutinto its surface that faces body 88 an exhaust passage groove I38 thatregisters with the end of exhaust passage H8 and that enters bore I21.It also has a supply bore I3I extended through it in registration withthe relay valve supply passage I26. A supply groove I33 cut into theinner surface of solenoid base structure 83 registers with bore I3I andenters bore I29 in axially spaced relation to groove I38. A controlledpassage groove I32 cut into the outer surface of cap plate 82, andcovered by base structure 83, opens at one end into bore I 21 betweenthe openings of exhaust and supply grooves I38 and I 33, and its otherend registers with the end of transfer valve bore 58. Groove I32corresponds to controlled line 59 of Fig. 1. The relay valve body is ofspool type, connecting controlled groove I32 to supply groove I 33 or toexhaust groove I38, depending on its position, and conseqently on theenergization or deenergization of solenoid 68. This arrangement providesthe type of transfer valve operation described above, the lands 48, 49acting in the end portions 53, 55 of bore 58 as pistons. When the relayvalve body is in its normal operating position of Fig. 7, bore portion55 is connected to passageway I88 through controlled groove I32, exhaustgroove I38, passage H8, and bore III, while bore portion 53 is connectedto the same passageway I88 by groove H3 in end cap 8|, passage H8, andbore III. Thus, although in normal operation, passageway I08 mayfluctuate between supply and exhaust as selected by the regulator orcontrol system, and static pressure of fluid in it may vary, pressuresapplied to valve lands 48, 49 are equal and bias spring 5I is effectiveto position the valve body- In anticreep position of the relay valve,when passageway 98 is connected. to a fluid pressure supply and.passageway I00. is connected to exhaust, transfer valve bore portion 55is connected to supply passageway 98 through controlled groove I32,supply groove iii, and supply bores l3! and [26, while bore portion 53remains connected to passageway loll. lThe pressures in bore portions53, 55 thereby are unbalanced and the transfer valve body is moved t itsanti-creep position.

From. the foregoing it will be seen that many changes. may be made inthe details of system and. apparatus arrangement within the scope of theinvention as defined. by the claims.

I, claim:

1. A hydraulic system comprising a reversible power unit provided withan external output member movable in opposite directions. by-delivery ofhydraulic power fluid. to one orthe other of two power unit inputs, apair of control lines: respectively connected to said inputs, aregulator device. for: selectively delivering power fluid to one or theother of said lines, a creepcontrclling auxiliary hydraulic supplysystem including an input supply line, a pair or output lines. connectedrespectively with. said. power unit inputs and an auxiliary regulatordevice having outputs respectively connected with: said output; linesand a. control element movable in opblocking said auxiliary system inputsupply line from communication with said control lines, and acreep-control condition blocking communication between said controllines and Power unit inputs and connecting said input supply line with apreselected one of said control lines, and a clutching .deviceconnectedwith said auxiliary regulator device control element andselective- 1y actuable between a disengaged condition and an engagingcondition mechanically connecting said control element to said powerunit output element for movement of the former with the latter and. in adirection to supply fluid to the power unit input, in a sense to movesaid output element opposite to that in which the output element: movesin, so actuating said control element. I

. 2. A hydraulic system according to claim. 1, in-

cluding common actuating means for said transfer valve and clutchingdevice and arranged to correlate transfer valve actuation to its.normal- .operation and creep-controlling conditions: with actuation ofthe clutching. device to its disengaging and engaging conditions;

3'. In a hydraulic system that includes a piston and cylinder power unitprovided with an. ex-

ternal member that moves with the piston ofthe unit, a pairof mainhydraulic flow lines. com- 'municating with opposite ends of thecylinder of the unit, and a regulator deviceconnected with said linesand: actuable between conditions for respectively connecting said;lines. in reversed senses to a fluid supply and an exhaust; means forpreventing substantial creep of the piston from: a selected position,comprising means for connecting a preselected one of said main lines tosupply; an auxiliary fluid delivery control 1d system comprising anauxiliary input supply line, a pair of controlled lines respectivelyconnected with the power unit cylinder ends, and a control valveincluding. a. body movable in opposite. directions from a neutralposition blocking said controlled lines from said auxiliary input supplyline and exhaust to positions respectively connect.- ingv the different.controlled lines to said input supply line and exhaust line in reversedsenses, a transfer valve. including a valve body axially movable betweena normal operation position connecting said main lines respectively withopposite. ends of the power unit cylinder and blocking. said auxiliaryinput supply line and a creepcontrol position blocking said main linesfrom the cylinder ends. and connecting the auxiliary input supply linewith said preselected main line, actuating means for said transfer valvecomprising a piston movable in a bore and connected with the transfervalve body for moving the latter to one said position when pressure isexerted in said bore and a spring biasing said valve body to its otherposition, a. transfer valve relay including a relay valve movablebetween two positions each corresponding to one. of said transfer valvepositions and respectively connecting. said bore to said preselectedmain, line and to exhaust, a solenoid having an armature mechanicallyconnected to said transfer relay valve for moving it to one of itspositions when energized and a spring biasing said relay valve to itsother said position, a clutch. device. having an operator movable inopposite directions respectively to clutch and disengage said pilotvalve body to and from said power unit external member, a, secondsolenoid having its armature mechanically connected to said operator formoving. the latter in. one said direction when the solenoid. isenergized and a spring biasing the operator in the other direction, andcircuit means for energizing said solenoids including switching meansarranged to control such energization to correlate. relay valvecontrolled movement. of the transfer valve body to its normal.-operation and creep-control positions respectively,. with movement ofsaid clutching device operation in its disengaging and clutchingdirections.

4. A creep-control assembly for a hydraulic power unit. provided with apair of power fluid inlets. and operable in reverse directions bydelivery of power fluid to one or the other inlet,

said assembly comprising a body structure having. therein a transfervalve bore and a control valve bore,. a. pair of main input passagewaysconnecting a pair of external. input openings with. a pair of spacedmain input valve ports opening into said transfer valve bore and a pair.of main. output passageways connecting. a pair of main. output openingswith a pair of main controlled ports opening into said. transfer valvebore. in spaced relation to each other and to said main input ports,said body structure. also having. therein. an auxiliary control valvesupply passage. connecting a controlled. port entering said transfervalve bore in spaced. relation to said main ports, and an exhaustpassage communicating with a. first one of said main input passageways',said auxiliary supply and exhaust passages respectively communicatingwith. supply and. exhaust ports entering said control valve bore. inspaced. relation, said, body structure. also having therein. a pair ofauxiliary output passages respectively connecting said. main outputpassageways with controlled ports; entering said cation between all saidmain ports and providing communication between said auxiliary controlledport and the second main input passageway, a control valve body movableoppositely in said control valve bore from a neutral position blOckingcommunication of said controlled ports with said supply and exhaustports and positions respectively connecting the different saidcontrolled ports with said supply and exhaust ports in reversed senses,said control valve body having an operator projecting from said bodystructure, and mean connected with said operator and selectivelyactuable to couple and uncouple said operator to and from an externalmovable element actuated in opposite directions by a reversiblehydraulic power unit.

5. A creep-control assembly according to claim 4, wherein said transfervalve ports are axially spaced along the transfer valve bore, saidtransfer valve body is axially movable in its said bore and is providedwith a body portion movable as a piston in an end reach of said bore,said assembly with the said second main input passageway and with asupply port of said relay valve, and a relay exhaust passage connectingan exhaust port of said relay valve with said auxiliary exhaust passage,said relay valve having a valve body actuable selectively to connect therelay valve controlled port with either said relay valve exhaust orsupply port.

6. In a hydraulic system that comprises a power unit having two fluidinputs, a regulator for delivering pressure fluid selectively and atvariable pressure to one or the other of two outputs and exhausting theother said output, and a pair of lines connecting said outputsrespectively with said power unit inputs; a valve including a valve boreinto which open a pair of input ports respectively connected with saidlines and a pair of output ports respectively connected with said powerunit inputs, said valve having a valve body movable in said bore betweenpositions respectively providing and blocking communication betweencorresponding pairs of said input and output ports and having axiallyspacedportions slidable in end portions of said valve bore as pistons,an auxiliary device selectively actuable by a movable actuating memberto and from a condition for supplying pressure fluid to a preselectedone of said lines and exhausting the other, a

v relay valve assembly comprising structure providing a valve chamberinto which open a controlled port connected with one said valve bore endportions, a supply port connected with said preselected line and anexhaust port connected with said other line, a relay valve body movablein said valve chamber between positions respectively connecting saidcontrolled port with said supply and exhaust ports and an actuatingmember movable to move said relay valve body between its said positions,a hydraulic line connecting the opposite said valve bore end portionwith one of said lines, and common operating means for said auxiliarydevice and relay valve actuating members arranged to correlate actuationof said device from and to its said condition respectively with movementof the relay valve body to connect said control port to the same line assaid other valve bore end portion is connected and to connect it to theother said line.

7. In a hydraulic system that comprises a power unit having two fluidinputs, a regulator for delivering pressure fluid selectively and atvariable pressure to one or the other of two outputs and exhausting theother said output, and a pair of lines connecting said outputsrespectively with said power unit inputs; a valve including a valve boreinto which open a pair of input ports respectively connected with saidlines and a pair of output ports respectively connected with said powerunit inputs, said valve having a valve body movable in said bore betweenpositions respectively providing and blocking communication betweencorresponding pairs of said input and output ports and having axiallyspaced portions slidable in end portions of said valve bore as pistons,an auxiliary device having outputs respectively connected to said linesand selectively actuable by a movable actuating member to and from acondition for supplying pressure fluid to a selected one of said linesand exhausting the other, a cutoff valve arranged in said lines betweensaid regulator and auxiliary device outputs and actuable by a movableactuating member between conditions respectively blocking and permittinflow of fluid between said regulator outputs and lines, a relay valveassembly comprising structure providing a valve chamber into which opena controlled port connected with one of said valve bore end portions, asupply port and an exhaust port connected with said other line, a relayvalve body movable in said valve chamber between positions respectivelyconnecting said controlled port with said supply and exhaust ports andan actuating member movable to move said relay valve body between itssaid positions, a hydraulic line connecting the opposite said valve boreend portion with one of said lines, and common operating means for saidauxiliary device, cutoff valve and relay valve actuating membersarranged to correlate actuation of said device from and to its saidcondition respectively with actuation of said cutoff valve to and fromits flow blocking condition and with movement of the relay valve body toconnect said control port to the same line as said other valve bore endportion is connected and to connect to the other said line.

8. A creep-control assembly for a hydraulic power unit provided with apair of fluid inputs delivery of fluid to the different ones of whichoperates such unit in opposite directions, said assembly comprising abody structure having extended therethrough an opening through oppositeend surfaces a transfer valve bore, a control valve bore and an exhaustpassage, and said body structure having therein a relay valve pocketopening through one said end surface, said body structure also havingtherein main line supply and exhaust passageways opening through alateral surface of said structure and through spaced line ports in saidtransfer valve bore and main line ports, said body structure also havingtherein a control valve supply passage opening into said transfer valvebore through a controlled port and into said control valve bore througha supply port, a relay valve supply passage opening through the same endsurface as said relay valve pocket and into said line supply passageway,auxiliary power unit passages respectively connecting control valvecontrolled ports that enter said control valve bore on opposite sides ofsaid supply port, a passage connecting said exhaust passage with saidline exhaust passageway, and passageways connecting with said exhaustpassage a pair of control valve exhaust ports that enter said pilotvalve bore in spaced relation to said control valve supply andcontrolled ports, a transfer valve body axially movable in said transfervalve bore between a position connecting together said line and powerunit supply ports and said line and power unit exhaust ports andblocking said transfer valve controlled port and a position blockingcommunication between said line and power unit ports but connecting saidtransfer valve controlled port with said line supply port, said transfervalve body having a pair of axially spaced portions respectivelyslidable as pistons in reaches of said transfer valve bore respectivelyadjacent said body structure and surfaces, a cap structure secured incontact with said end surface through which said valve pocket opens andcloses said passages and valve bores and with said valve pocketproviding a relay valve chamber, said body and cap structures beingprovided with opposed surfaces and grooves providing closed passagewaysthat respectively connect the end of said transfer valve bore with arelay valve controlled port in said relay valve chamber and said supplyand exhaust passages with relay valve supply and exhaust ports in saidchamber, a relay valve body movable in said chamber between positionsrespectively connecting said relay valve controlled port with said relayvalve supply and exhaust ports, a second cap structure overlying theother said body structure end surface and closing said valve bores andexhaust passageway, said body and second cap structures being providedwith opposed surfaces and grooves enclosing bleeder passages that extendbetween said control and transfer valve bores and said exhaust passage.

9. In creep control means for a hydraulic system that includes areversible power unit provided with an external output member movable inopposite directions by delivery of hydraulic power fluid to one or theother of two power unit inputs, and a regulator device for selectivelydelivering power fluid to one or the other of said inputs, said creepcontrol means comprising, in addition to said regulating device anauxiliary valve movable in opposite directions respectively to deliverfiuid to the different ones of said two inputs and a member movablebetween first and second conditions respectively connecting anddisconnecting said control valve to and from said output -memberrespectively to establish anticreep and normal power unit control,supply means for delivering power fluid to said control valve, ablocking device aotuable between first and second conditions whereinrespectively it blocks and establishes delivery of power fluid to saidcontrol valve, cut oif means actuable between first and secondconditions respectively permitting and blocking delivery of fluid tosaid inputs by said regulator device, and common control means arrangedselectively either to simultaneously actuate both said blocking and cutoff devices to their said first conditions and move said member to itssaid second condition, or to simultaneously actuate both said devices totheir said second conditions and move said member to its said firstcondition.

STANLEY A. JACQUES.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 552,811 Batchelor Jan. 7, 1896 1,742,892 Belcher Jan. '7, 19302,016,727 Roth Oct. 8, 1935 2,220,180 Spitzglass Nov. 5, 1940 2.409.517Schmit Oct. 15, 1946

